It is a problem that there is no reliable way of measuring the arching in general of an elongate body and in particular of a ski. In this context, an elongate body may, for instance, be different types of boards, beams, leaf springs, masts, pillars, posts, shafts, etc. Below, the description is focused on skis.
Nowhere there is two exactly similar skis, they are all individuals, since they are constructed as laminates consisting of composite and core material. Variables determining the properties of a ski based on substantially a composite material, as, e.g., arching curve, stiffness of a ski, is type of fibre, content of fibre, matrix material, direction of reinforcement, core material and the adhesion between each material layer. Additionally, there are also the production conditions with all the varying parameters and the influence thereof on the final product.
Skis are produced by a pressing method where heat and pressure are introduced in the manufacture. The product and the material are created simultaneously, and natural variations are present that may be found in the finished final product. It always varies, but the size of and the extent of as well as the reason for the variations may be different between the skis. Skis may “be tailor-made” by theoretically dimensioning and constructing versus a certain stiffness and/or for obtaining a certain specific arching curve.
However, a difficulty is to measure and define an arching curve in the production. When the skis have been delivered to retailers, it is not possible to measure the arching, since measurement methods are lacking there. Lack of a clearly defined arching curve is a problem. Correct arching is spoken of, but it is not possible to display it graphically neither to define it at all. Neither there is any possibility of comparing the arching curve between an existing pair of skis for a specific snow condition, with the purpose of being able to sort out or distinguish a pair of new skis in a controllable way having specifically corresponding or specifically other properties.
The following actors represent the great interest:
Skiers, trainers, waxing-responsible persons, manufacturers, wholesale dealers, retailers.
Among skiers within the world elite, elite amateurs, amateurs, there is a great interest to be able to determine an arching curve specifically. This is for getting a possibility of optimising the relation between the sliding surface of the ski and the part of the ski that is coated with different waxes, with the purpose of providing grip upon the depression of the skier in an upward slope.
Among all skiers in the world, it is apprehended as the crucial thing to try out the correct arching for each skier. The curve of the arching affects, among other things, the length and the position where the grip wax should be coated on the running surface.
Elite skiers are occasionally forced to try up to a hundred of different skis before they can identify two skis that have similar properties and similar arching curve.
Today, two skis are placed beside each other on a planar ground, preferably indoors. The skier stands on the skis with the body weight evenly distributed between the two skis. The skier transfers the body weight to one of the skis with the purpose of trying to imitate the situation when you are skiing and intend to “tread” down the arching into contact for getting grip with the wax, after which the following is carried out:
A feeler gauge, usually 0.2 mm high, is brought by a hand from the rear part of the ski and forward until it “feels” like there is resistance and “sucks a little”. After this operation, an approximate wax length is recommended empirically and arbitrarily, from the heel and forward to the approximate point of the ski where the feeler gauge contacts the ski, or it is recommended to try out another ski, etc. The skier then presses down the ski extra hard with the purpose of checking if the feeler gauge of 0.2 mm can be clamped, since this then should imitate when the same in the track treads down the ski into contact for providing grip by the fact that the grip wax meets the ground.
This is the method applied today in shops, at trainers and at other interested parties around the world.
In factories, it is, by means of traditional industrial measuring machines that are available in certain factories, possible to determine the measures of the arching by, e.g., a measuring probe. However, the different existing methods and machines are very expensive, involving investment levels of the order of hundreds of thousands of Swedish crowns up to millions. Furthermore, the method is very slow, which means that not all skis can be classified and marked because of the expense, no one or very few would buy them except for the world elite, which is forced to try ever so many skis, without knowing what kind of arching curve they have.
The experience and performance of the skier is substantially based on the arching, it is absolutely decisive and the basis for the skis to work at all and by grip wax applied under the arching be able to provide grip in an upward slope, simultaneously an optimally determined sliding surface.
NO SKIER KNOWS TODAY WHICH ARCHING CURVE IT HAS, SINCE THE CURVE/IMAGE OR THE CONCEPT DOES NOT EXIST AMONG THE SKIERS.
Not even at a producer of skis do two different persons know what is intended with arching curve or the mutual parameters thereof.
A diffuse so-called arching is something that is felt and experienced without dimensions or a clear description. Sometimes, the arching may be described as a linear measure, but it takes no consideration to the length at a specific load or the geometry of the curve as seen from the side at a specific load.
Examples of Consequences due to the Absence of an Efficient and Accurate Method to Determine and Define the Arching Curve
Consequences, it is not possible today to measure an existing ski that feels relatively good and determine how the arching should be altered for offering optimum experience or performance at specific conditions in the ski track. Only by practical evaluation in ski tracks and opinions as well as crude judgements and after a hundred of tests, a desired result may possibly be achieved.
For the shop, this is time-consuming and it affects the economical result since more employees are required when skis are sold.
The skier gets no grip in the track, which results in the skis sliding backwards and a poorer skiing experience, as well as that one may be forced to discontinue due to becoming tired earlier and not managing the entire intended distance. The result for competing skiers becomes substantially poorer.
One may experience poor glide due to the fact that one treads down the arching into contact upon too low a load and then the skis “are jamming” and the grip wax disappears fast by wear after which they “slide backwards.”
From the manufacturers to the retailers, there remain great stock volumes of skis that have not been sold because it has not been possible to try out and sell the same in a simple or fast way.
Everybody desires to be able to quickly and easily determine the very crucial arching curve with high accuracy, but no one can make this today easily, quickly or at low cost.